/*
 * deamonize.c
 *
 *  Created on: 2012-4-30
 *      Author: jawinton
 */

#include "apue.h"
#include<syslog.h>
#include<fcntl.h>
#include<sys/resource.h>

//extern void pr_ids(char *);

void daemonize(const char *cmd)
{
    //pr_ids("into daemonize");

        int i, fd0, fd1, fd2;
        pid_t pid;
        struct rlimit rl;
        struct sigaction sa;

        /* clear file creating mask */
        umask(0);

        /* get maximum number of file description */
        if(getrlimit(RLIMIT_NOFILE, &rl) < 0)
                err_quit("%s: can't get file limit", cmd);

    /* become a session leader to lose controlling TTYs */
        if((pid = fork()) < 0)
                err_quit("%s: can't fork", cmd);
        else if(pid != 0) //parent
                exit(0);
    //sleep(1);
        //pr_ids("after first fork in child");
        setsid();  //just in child process

        /* ensure future opens won't allocate controlling TTYs */
        sa.sa_handler = SIG_IGN;
    sigemptyset(&sa.sa_mask);
        sa.sa_flags = 0;
        if(sigaction(SIGHUP, &sa, NULL) < 0)
                err_quit("%s: can't ignore SIGHUP", cmd);
        if((pid = fork()) < 0)
                err_quit("%s: can't fork", cmd);
        else if(pid != 0) //parent
                exit(0);

        /* change the current working directory */
        if(chdir("/") < 0)
                err_quit("%s: can't change directory to /", cmd);

        /* close all open file descriptors */
        if(rl.rlim_max == RLIM_INFINITY)
                rl.rlim_max = 1024;
        for(i=0; i<rl.rlim_max; i++)
                close(i);

        /* attach file descriptor 0, 1, and 2 to /dev/null */
        fd0 = open("/dev/null", O_RDWR);
        fd1 = dup(0);
        fd2 = dup(0);

        /* initialize the log file */
        openlog(cmd, LOG_CONS, LOG_DAEMON);
        if(fd0 != 0 || fd1 != 1 || fd2 != 2) {
                syslog(LOG_ERR, "unexpected file descriptors %d %d %d", fd0, fd1, fd2);
                exit(1);
        }
}


